Subaqueous tunneling.



F. D. LEFHNGWELL.

SUBAQUEOUS TUNNELING. APPLICAHON FILED SEPT- 30. 19M.

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SUBAQUEOUS TUNNEUNG.

I APPUCATIUN man SEPT. 30. I914.

1,298,742. Patented Apr. 1,1919.

FIGS. I618 F. D. LEFFINGWELL.

SUBAQUEOUS TUNNEUNG.

APPLICATION FILED sum 30. 1914.

1 ,298,742. Patented Apr. 1, 1919.

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Patented Apr. 1, 1919.

F. D. LEFFINGWELL. su musous wu NG. APPLICATION FILED S'EI' l9l4. 1,298,742. Patented Apl 1,1919 Fl Q17. Fl (3:18.

FRANK D. LEFFINGWELL, OF MONTGLAIB, NEW JERSEY.

SUBAQUEOUS TUNNELING.

Specification of Letters Patent.

Patented Apr. 1, 1919.

Application filed September 30, 1914. Serial No. 864,217.

To all whom it may concern:

Be it known that I, FRANK D. LEFFING- WELL, a citizen of the United States, residing in the town of Montclair, county of Essex, and State of New J erscy, have invented certain new and useful Improvements in Subaqueous Tunneling, of which the following is a specification.

The object of my invention is to reinforce a subaqueous bed, enabling it to resist forces tending to alter its position or condition arising from tunneling thereunder.

The particular objects of my invention are to provide means and a method for holding the surface and subsurface material of a subaqueous bed in compact form when compressed air is employed in the tunnel-driving operations, so that as the tunnel heading is advanced, the overlying stratum of soil will be retained in its formation and its density maintained, rendering it as impervious as practicable to the escape of compressed air, and further to increase the natural weight over a projected tunnel heading without unduly decreasing the navigable depth of water.

With these objects in view I have devised an improvement in subaqueous tunneling by which, as the tunnel bore is advanced through the earth, the water-bed is progressively reinforced by a connecting series of ballasted sections comprising an overlying diaphragm whose character varies in accordance with the nature of the bottom to be reinforced and in accordance with the thickness of the stratum of earth between the water-bed and the tunnel arch, as more particularly hereinafter set forth and described.

In constructing a tunnel below the bed of a body of water, compressed air is commonly used to balance the head of water above the tunnel. This hydrostatic pressure may be measured either at the arch or at the axis, or at the invert of the tunnel. If merely the head of water from the arch to the surface of the water is balanced by the air pressure carried in the tunnel, an equilibrium pertains in theory throughout the column of water held in the stratum of soil between the arch and water-bed. This condition, however, leaves at the invert an unbalanced head equivalent to the tunnel diameter which, in sand, quicksand, gravel or other porous material, permits the inflow of water at the invert and tends to undermine both the heading and the adjacent completed portion of the tunnel. The air pressure in the tunnel must therefore be increased, and usually such increase must equal a head of water corresponding to onehalf the tunnel diameter. comes desirable to carry a still higher pressure of air, and any excess ressure thus carried increases greatly the itliculty and dan ger of subaqueous tunneling. The use of the term excess pressure herein used is intended to indicate the pressure of air carried in a tunnel heading above or in addition to the hydrostatic pressure of water at the tunnel arch. Coincident with any increase of pressure above that which will sufiice to maintain equilibrium at the arch, the water is driven back through the porous cover or stratum between the arch and water-bed, and the compressed air from the tunnel begins to escape through such material in a nearly vertical direction, loosening and disintegrating such stratum and eventually blowing off that part of the bed vertically over the arch, and tending to form a depression at this point in the shape of an inverted hell, with a resultantly rapid increase in the loss of air from the pressure chamber of the tunnel. It has been noted that the initial escape of compressed air through a given cover is opposed and checked in a considerable degree by said cover, which continues to oppose and check such egress of air until such time has elapseo as will result in said cover becoming jarred, shaken, loosened, disintegrated, eroded, or aerated, by the force designated as excess pressure, impelling air and water therethrough. It becomes desirab e, therefore, to oppose such vertical disturbing force by suitably adjusted and weighted diaphragms above the tunnel heading, the weights re quired in said diaphragms being directly proportional to the excess head carried in the tunnel and inversely proportional to the depth of overlying cover of a given material.

The method hitherto relied on to diminish the above noted excessive loss of air and to avoid flooding the tunnel through a blowout, consists in floating barges of clay to a point on the water surface vertically over At times it be' the arch of the tunnel heading and dumping the clay, to form a protective blanket on the water-bed. Such clay blanket, having some tenacity, tends to check the vertical loss of air, while the earth cover itself, comprising the stratum of the waterbed above the tunnel, although it may be porous, noncoherent, and ineffective against air pressure, applied from below, yet opposes a fairly e ective resistance to any lateral movement of the air. A clay blanket, however, especially in a tidal stream, is rapidly wasted away by the combined influence of moving water and escaping air. Consequently, in any reinforcement by clay or like material, great difficulties have been encountered, arising from the above described tendency of the .clay to become dissipated, resulting in blow-outs, endangering the safety of the work and the lives of the workers.

The method which I have devised attains the objects of my invention by opposing vertical loss of air and consequent disturbance of the material overlying the tunnel and heading, and consists in the interposition of a relatively tenacious diaphragm member comprising a series of diaphragms, preferably of greater width than the tunnel bore and extending both in advance of the tunnel heading and over such part of the completed tunnel as may be advantageous. This diaphragm member thus interposes a resistance to the vertical loss of compressed air, causing such air to pass laterally through a space such that the lateral resistance of the soil or friction head plus the head above, representing the hydrostatic pressure from the water surface to the tunnel arch, shall be slightly less than the pressure required in the tunnel.

This method accomplishes the further result of opposing the lateral flow of air, by the use of suitable planes extending downward from the said diaphragms, these vertical planes or baflles extending both longitudinally and transversely to the tunnel in this embodiment, along the edges of the said diaphragms.

These means accomplish the further result of enabling weight to be added over a projected tunnel heading without unduly decreasing the navigable depth of water, such means comprising another construction of said diaphragm employing the use of beams or truss members suitably connected. the diaphragms being placed at a plane below thenatural bed of the water. the removed cover being replaced by a weight, such weight consisting either of materials transported for the purpose, or of the silt and sand of the riverbed refilled to its natural level. This principle of reinforcement is particularly adapted to use in cases of extremely shallow cover by the location of the weight below the level of the diaphragm along its lateral margins, thus enabling a subaqueous tunnel to be safely constructed with a minimum depth of cover, while overcoming the tendency of the tunnel to float.

In the accompanying drawings I have illustrated the preferred embodin'ients of means for practising my invention. Throughout these drawings like reference numerals indicate corresponding parts in the several views.

In these drawings, Figure 1 is a vertical section through one unit of a water-bal lasted diaphragm positioned upon the water-bed over a cross-section of the tunnel on line II of Fig. 2-; Fig. 2 is a vertical section on line II--II of Fig. 1, showing a series of units. the two central units being in operative'position, that to the left being shown. as in course of removal. and that to the right being shown in course of setting, by being lowered into place; Fig. 3 is a top view of one unit and of a part of another, illustrating the means of jointure between them; Fig. 4: is a detail sectional view of a portion of the dia phragm showing the means forventing the Water trapped thereunder when the diaphragm is being positioned, such means permitting the inflow or injection of water when the diaphragm is to be withdrawn; Fig. 5 is a detail section of portions of two adjacent diaphragms showing a supplemental detachable baffle connecting their opposed ends; Fig. 6 is a view similar to Fig. 1 of a modified form of structure taken on line VIVI of Fig. 7, in which the unit is constructed in part of wood, instead of metal, as shown in Figs. 1, 2 and 3; Fig. 7 is a vertical sectional view on line VI-Vl of Fig. 6, corresponding generally in its relation of the units to the arrangement shown in Fig. 2; Fig. 8 is a top view of the unit shown in Fig. 6 and of means of connecting adjoining units, Fig. 9 showing a detail of the separable side flange and its method of connection to the unit shown in Fig. 6; Fig. 10 shows a type of unit, on the line X.X of Fig. 11, constructed of reinforced concrete in general arrangement similar to the views shown in Figs. 1 and 4. Thethree types shown in Figs. 1, 6 and 10 are adaptable to the varying conditions of bottom encountered; Fig. 11 is a View in vertical section on the line XIXI of Fig. 10. similar in its general arrangement to the construction illustrated in Figs. 2 and 7, showing in section a joined series of concrete units: Fig. 12, like Figs. 3 and 8. illustrates a single unit, in this instance of the concrete type of Figs. 10 and 11, and the method of its attachment to an adjacent unit; Fig. 13 is a vertical section on line XIII-XIII of Fig. 14. illustrating my improved reinforcing diaphragm adapted to conditions of shal- 10, 11 and 12, showing a concrete joint between the sections of the diaphragm.

In the preferred embodiment of my invention, each unit of the reinforcing diaphragm comprises an air-tight chamber of a Width substantially twice the diameter of the tunnel and of a length substantially half its width, provided with downwardly projecting side flanges and two intermediate like flanges positioned apart approximately the width of the tunnel. The end of each unit is formed to engage the opposed end of the next unit in series in frictional engagement, and the sides as well as the ends of each unit project upwardly from the chamher to form a continuous peripheral flange for retaining additional ballast to supplement that furnished by the contained water.

Referring to the drawings in detail, the numeral 1 designates the water, 2 its bed, 3 the bore of the tunnel, 3, a source of compressed air and 4 a section of the diaphragm. Each unit section comprises a chamber 5 having at each side a pair of valves 6 for the control of air therein, and a pair of valves 7 for the control of water therein; also a valve 13 on a pipe 12 having the openings 11 through the bottom of the diaphragm to permit the withdrawal of water from beneath the diaphragm when it is being positioned, or the admission or injection of water when it is to be raised. The bottom of each unit section has the downr-xardly projecting side flanges or baflies 8, 8 and the intermediate central flanges or baffles 9, 9 and the top of each has the upwardly projecting peripheral flange 10.

Referring particularly to Figs. 1, 2, 3, 4 and 5, the unit section is there shown as constructed of metal, preferably boiler plate, its ballast chamber 5 being stiffened by trussing 14 and the angle irons 15 supporting the flanges. The front wall 16 of the chamber of each unit is sloped rearwardly from bottom to top, and the rear wall 17 is formed at an angle at the point 18 where it joins the floor of the chamber, the wall above the floor sloping forwardly from bottom to top, and the flange 19 below the floor sloping forwardly from top to bottom below the level of the floor. Forwardl projecting side flanges 20, shown in Fig. 3, flare outward from the forward wall of the chamber, serving as lateral guides, adapted, when one unit is in position, to receive the next vided for engagement with a. hook 22 and tackle 23 for raising and lowering these units.

The operation of the embodiment of my invention illustrated in Figs. 1 to 9, inclusive, consists in floating each unit to the place where it is to be sunk, and opening the water valve to the ballast chamber, permitting the entry of water to replace the air which is allowed to escape through the air port 6. When the chamber has been filled with water, it is lowered into place by suitable tackle, the valves 13 being opened to allow the escape of the water trapped below the chamber and between the bafiie-flanges, these valves being then closed. Each unit section is successively positioned in advance of the heading, as shown in Fig. 2, and fitted against the last preceding section located, the end and side flanges of each unit and the intermediate flanges as well entering the earth and forming lateral reinforcements to oppose the dissipation of the earth between them. As the tunnel heading is advanced sufliciently beyond a given section, those seo tions to its rear may be successively withdrawn by suitable tackle. Upon with- 100 drawal, the valves 13 are first opened to permit the inflow or injection of water beneath the diaphragm, then the water cocks 7 are opened, when, upon the opening of the air valve 6 and air under pressure being ad- 1 mitted, the water ballast is forced out. If the nature of the soil is found to be such as to require greater force to cause the baffle flanges to enter to their full depth, this may be accomplished by means of a pile-driver or 110 the like.

In Figs. 17 and 18 the method of opposing the flow of air from the tunnel is shown more clearly by diagram. Point A indicates a point on the surface of the water at mean- 115 high water. B indicates the position of a weighted diaphragm on the waterbed. 0 represents the arch of the tunnel, D a point on the axis. In Fig. 17 it will be noticed that the diaphragm extends laterally with as in the case of the lateral positioning thereof, in accordance with the depth of cover and the nature thereof.

In carrying out the method indicated in the diagrams, the diaphragms are conveyed to a point above the tunnel heading, and preferably those of the pontoon type are laid first. The diaphragm may be suspended above the heading by any convenient means, and while so suspended is positioned, so that when finally sunk it will lie in proper position on the waterbed.

The diaphragm may be adjusted laterally with respect to the heading first, so that its center is practically in line with the axis of the tunnel and so that its width will overlap the sides of the tunnel by a distance ap proximately equal, as shown here, to half the diameter of the tunnel. Having made this adjustment, the diaphragm may then be adjusted longitudinally with respect to the walls of the tunnel and so positioned that the rear portion overlaps the tunnel heading and the front portion projects therebcyond. The amount of lateral projection and longitudinal projection and overlapping must be determined beforehand by a consideration of the nature and depth of the cover and the proposed excess pressure in the tunnel.

These adjustments having been effected, the pontoon may then be sunk in place by opening the valves 6 and 7 and admitting the water into the chamber of the pontoon, as heretofore stated. The pontoon is then sunk into place. It will be noted that the pontoon diaphragms are preferably used near the shore and that the concrete diaphragms hereinafter mentioned might advantageously be employed toward the center of the water-bed. The matter of positioning the concrete diaphragms is carried out in substantially the same way as the pontoon diaphragms. Having positioned either type of diaphragm, the next step is to secure it, sufficient weights being employed in order to prevent the diaphragm from rising, due to the excess pressure carried in the tunnel.

The lateral and longitudinal adjustments mentioned and the weights employed are directed to oppose the flow of air laterally and vertically from the tunnel heading. It will be readily understood that this flow of air will vary in accordance with the nature of the material through which it must pass to reach an outlet, and also the depth of this material. The method described is not designed to effect a complete retention of air by the diaphra m and its bafiie plates, but is rather designer to oppose and retard this flow of air so as to reduce it to a comparatively small amount. It will be noted that by opposing the vertical flow of air from the tunnel, thereby the erosion which would result by forcing the water through the cover material ahead of the air is practically revented. In this connection it is also to lower edges of the downwardly projecting flanges 24: of the respective diaphragm sections, the shank 27 extending upwardly from the base 26 to a transverse arm 28 and terminating in a ring, to which is fixed a chain and hook 30. The hook and chain serve to hold this detachable bafile in place, while admitting of some relative movement of the two adjacent sections to which it is marginly attached, such motion being limited by the transverse arm 28. When one section is to be withdrawn, after completion of the tunnel heading thereunder, the chain may be detached therefrom and attached to the other section. This supplemental ba'liie serves as a sealing medium between adjacent sections, when. due to the nature of the water-bed, it may be found advantageous to form marginal flanges of opposed inclination converging at the bottom, so as to admit of greater play between units of a series. Clay or suitable material properly confined may be placed within the marginal baffle or between adjacent diaphragm units.

Next referring particularly to the adaptation of my device shown in Figs. 6 to 9, inclusive, intended for use upon bottoms of softer character: The sectional chamber 5 is provided, as before explained, with valves for filling it with water ballast and for emptying it, and with eyes 81 for the attachment of suitable tackle. In this construction the sectional units are built of wood and are provided with the separate metal side flanges 8, 8 having the heads 32, adapting them to be driven down by independent means to such depth as may be desired, these flanges being slotted to accommodate the stems of the valves 6 and 7. Each section is provided with flanges 33, permitting the close union of one section to another, each being guided into place by these flanges, the alinement being further preserved by the separable side flanges 8, 8, which with the end flanges 34 and the intermediate flanges 9, 9 serve to form compartments for reinforcing the bed and opposing its dissipation by escaping air.

In the modification of the invention disclosed in Figs. 10, 11 and 12, the numeral 35 designates a diaphragm of reinforced concrete having the side flanges 8, 8 and the intermediate flanges 9, 9 and the upwardly projecting flange 10, and the forwardly projecting guide flanges 36, and the hinge members 37 and 88 united by the pins 39. As shown in Fig. 11, the forward end of each unit comprises a headed portion projecting both upwardly and downwardly, its forward faces being rearwardly inclined from the hinge, while the back portion of each unit has an upwardly projecting headed portion forwardly inclined fror: the hinge. These angles of inclination admit of the hinged units being joined together, the baflle flanges 8, 9 and 31 carried by each entering the soil upon the load of ballast 39, here shown as concrete slabs, being placed on the roof of the diaphragm bounded by the flange 10. Under certain circumstances this ballast might be dispensed with. The peripheral baflie flanges form a retaining compartment subdivided by the intermediate flanges 9, 9 into a number of compartments whose walls prevent the dislodgment of the soil, as in the other constructions.

In the modification illustrated in Figs. 13 to 15, in lusive, the adaptation of my means to a shallow cover is shown. Each unit in this construction has ballast chambers 40 spaced apart slightly beyond the width of the tunnel and forming between them an air trap, their depending flanges 41 serving to supplement the reinforcement afforded by the compartments themselves. Each of the units is adapted to be movably jointed to its neighboring units by the knuckles 37 and 38 and pintles 39, the pintles passing through the holes in the inwardly sloping guides 36. In this application of my invention. the sectional diaphrag is positioned below the watenbed, and the additional weight necessary to prevent the tunnel from floating is lo alized in the marginal pockets or ballast chambers 40, enabling the tunnel head to be driven, where otherwise the shallowness of the cover would be prohibitive.

In Fig. 19 a modified means of securing the concrete members35 together is shown. They are provided on their adjacent flanges 10, 10 with recesses, preferably centrally disposed. The concrete members are positioned in substantially the same manner as heretofore noted, and when so positioned and weighted, as by concrete blocks 42, the concrete mixture mav be poured in between to form a bond 43. This con rete mixture may of course be replaced either partially or wholly by concrete in-bags, or by a clay and concrete bond, or other suitable materials.

The term relatively tenacious, used herein, is intended to indicate a material whose cohesiveness is relatively greater than clay and under ordinary circumstances would in clude wood. iron or steel. concrete, and other similar substances, and certain kinds of fabric.

Having thus described the preferred embodiinents of means for practising; my in vention, which are susce tible of variation through a wide range 0 equivalent structures, but without desiring to be limited in the scope of the application thereof to the pre ise constructions shown and described, I claim:

1. Means for protecting a tunnel heading employing compressed air from damage by the destructive effect of the air escaping therefrom comprising an impervious diaphragm adapted to be positioned upon the soil overlying the tunnel heading and to contact superficially therewith throughout the overlying area, means for Weighting said diaphragm to produce distributed pressure dire tly upon said soil, and means for preventing the free movement of air beneath said diaphragm consisting of a plurality of baliles downwardly projecting from said diaphragm and adapted to penetrate the surface of said soil over and about said heading.

2. In combination, a source of compressed air exerting pressure in a tunnel heading, a plurality of sealing diaphragms adapted to be progressively positioned above the tunnel heading, said diaphranms having flat bottoms and downwardly proiecting Walls adapter to enter the bed and to regulate the flow of air from the tunnel heading. and means for adjustably ballasting each of said diaphragms.

3. In combination, a source of compressed air exerting pressure in a tunnel heading and a series of fiat metal sealin dianhra gms adapted to be progressivelv positioned above the tunnel heading, said diaphran'ms having downwardly proje ting side walls adapted to enter the bed and to regulate the flow of air fromlthe tunnel heading.

4. A. se tional overhead diaphra m for subaqueous tunneling comnrisinn a plurality of deta 'hablv -onnected units. each u t having downwardly proie ting marginal flan es adapted to enter the subariueous soil and to form an air-tioht reinfor ement to said soil against vertical or lateral displa ement. and means forcom ectiue a iacent flanges comprising a deta hable baflie.

5. A sectional reinforcinq diaphragm for subaoueous tunneling. each se tion b ing marginally ioincd o the adio ning se"t ons bv deta hable bafiles deta hablv eno'aning the adia e t edges of each pair of se tions.

6. A. sectional reinforcing and sealing diaphrasrm for subaqueous tunneling comprising interfitting sections. each se tion having a portion for proiection into the river-bed, and a bond forming a ioint between the portions adapted to so project.

7. The method of subaqueous tunneling which comprises substantially pre enting the verti al movement of air or fluid from the tunnel heading by sealino; the overlying soil thereagainst and limiting the lateral flow from the heading by interposing ver tical diaphragms of relatively tenacious material constituting lateral baifles above the projected or completed points of the tunnel heading.

8. In subaqueous tunnel construction, a source of compressed air producing emess pressure in a tunnel heading, said heading, an impervious weighted diaphragm member thereover, and means for proportioning the weight of said member to overcome the excess pressure in the heading, said member being adapted to seal the surface of the water-bed against the destructive tendency of the air escaping from the tunnel hea ing, said member having downwardly extending laterally distributed members adapted to be ositioned above and about the tunnel headmg to obstruct the flow of air therefrom in all directions beneath said diaphragm.

9. In the art of subaqu'eous tunneling employing air under such compression as to produce exeesspressure in the tunnel heading, the method of preventing blowouts consisting in interposing between the tunnel heading and the water a horizontal means to increase the frictional resistance of the soii penetrated by said tunnel to the passage of compressed air escaping from the tunnel heading, and vertical means adapted to increase the distance such air must travel to reach the water-bed.

10. In subaqueo-us tunneling in the pres ence of compressed air, a continuous horizontal diaphragm adapted to contact throughout its under area with the water had and weighted to exceed the predetermined li-ftirrg force of wmpressed air in said tunnel, and means on the under surface thereof to impede the flow of fluid therealorrg, said means comprising downwardly extending planes bafiles both to longitudinal and transverse flow.

11. ln subaqueous tunneling, a heading contain" air under compression, and means fopjnaintaining constant in the overlying soilitgqmrmal frictional resistance to the e ca .ef-ai "f om said heading, comprising a so d diaphragm member adapted to contact throughout itsunder area with the surfaggtgfi the water hed and of greater width than,:the tuiifiiql, boieand extending over said-hone adjacent said heading and in adnce hea ing M d hav g dep int, he apted to 141 dc the transverse flow gai enea h sa d diap ra 12; hev method of subaqneous tunneling employing air under such compression asto produce excess pressure in the tunnel headmg consisting in superposing upon the water-bed, and in surface contact therewith throughout the area overlying the tunnel heading, a tenacious diaphragm impervious to air; weighting same; and inter osing vertical members below said diap ragm adapted to preserve the unit frictional resistance of the soil penetrated by said tunnel to the passage of compressed air escaping from t e tunnel heading by preventing vertical localization of the air flowing therefrom.

13. The method of subaqueous tunneling employing air under such compression as to produce excess pressure in the tunnel heading comprising the positioning of an overlying horizontal seal in contact throughout with the Water-bed; inserting a series oi vertical seals forming hermetic joints with said horizontal seal into said bed; and inserting another series of vertical scale in said bed angularly disposed to the firstnamed series and Kenning hermetic joint therewith adapted to build up a countervailing pressure exterior to the tunnel heading tending to equalize the excess pres-lure in said heading by trapping the escaped air in the soil above said heading.

14. The method of subaqueous tunneling consisting in employing air under compression to produce excess pressure in a tunnel heading: sealing the Water-bed in a zone overlying the tunnel heading; weighting same in inverse proportion to the depth of cover betweenhthe water-bed and the heading and in direct proportion to the excess pressure iand interposing resistances in the soil bet veen the sealing member and the heading adapted to divert the flow of air escaping under excess pressure from the tunnel heading and to distribute its effective pressure.

15. The step in the method of subaqneous tunneling employing air under compression capable of producingexcess pressure which. consists in preventmg vertical localization of fluid pressure within a zone about to be penetrated by a'tunnel by interposing horizontal and vertical media adapted to distribute such ressure over a wider area.

rain; 1). LEFFINGWELL.

Witnesses:

Qm s Wnmus, J. B. L. Clams,

r e! qtt is re est may be shunned r fi e en s ch by ddressing e .cq m aaionfi 0 new, Va uatio D 0." 

